Limiting contamination in waste disposal wells

ABSTRACT

Contamination of underground aquifers by waste materials injected through disposal wells is limited by injecting a mobility buffer ahead of the waste material. The mobility buffer is an oil-external or water-external micellar dispersion having sufficiently low mobility to inhibit fingering of the waste material. A more favorable mobility ratio can be achieved by injecting a series of consecutively mobility graded dispersions into the aquifer.

United States Patent Poettmann LIMITING CONTAMINATION lN WASTE DISPOSALWELLS Inventor: Fred H. Poettmann, Littleton, Colo.

Assignee: Marathon Oil Company, Findlay,

Ohio

Filed: Mar. 29, 1971 Appl. No.: 129,180

Related US. Application Data Continuation-impart of Ser. No. 873,669,Nov. 13, 1969, Pat. No. 3,606,925.

US. Cl. ..l66/305 D Int. Cl ..B65g 5/00 Field of Search..l66/274, 292,294, 273, 305 D,

[111 3,722,593 1451 Mar. 27, 1973 [S6] Relerences Cited UNITED STATESPATENTS 3,493,051 2/1970 Gogarty ..l66/274 3,380,522 4/1968 Payne, Jr.et al. 166/292 X 3,400,761 9/1968 Latimer, Jr. et al. ..l66/274 PrimaryExaminer-Stephen J. Novosad I Attorney.loseph C. Herring, Jack L. Hummeland Richard C. Willson, Jr.

[57] ABSTRACT 13 Claims, No Drawings LIMITING CONTAMINATION IN WASTEDISPOSAL WELLS CROSS REFERENCES TO RELATED APPLICATIONS This is acontinuation-in-part of copending application identified as Ser. No.873,669, filed Nov. 13, 1969, now U. S. Pat. No. 3,606,925.

BACKGROUND OF THE INVENTION 1. Field of the Invention This inventionrelates to the disposal of waste materials into aquifers and tocontaining these waste materials within a given perimeter by usingmicellar dispersions as mobility buffers. The micellar dispersions areinjected ahead of the waste materials to inhibit fingering of the wastematerials out into the aquifer.

2. Description of the Prior Art Disposal of waste materials into freshwater aquifers often presents magnified contamination problems sincewaste materials, particularly aqueous waste materials, often tend toseek out and establish channels within the fresh water aquifer. Thesechannels may finger out" in such a fashion and at such a rate thatportions of the fresh water aquifer removed from the injection well maybe contaminated long before the major portion of the waste materialreaches that distant point. This fingering effect is due to the factthat waste materials are often more mobile thanthe waters of theaquifer, therefore these higher mobility waste materials tend to diffuseto distant parts of the aquifer faster than the water originally in theaquifer.

U. S. Pat. No. 3,380,522 teaches a methodof inhibiting the horizontaladvance of saline water into fresh water aquifers by injecting intothese aquifers a slurry containing granular materials such as reclaimedoil well drilling mud and sedimentary clays. The patent claims that suchmaterials form an impermeable bridging mass in the aquifer and therebyblock the intruding contaminating waters. Although this method mayeffectively block the outflow of contaminating materials into a freshwater aquifer, it limits the volume of the aquifer available in disposalwell applications by effectively confining the aquifer to a fixedvolume.

The object of this invention is to create a mobile piston-like mobilitybuffer within the aquifer which can expand as more waste material isinjected behind it and yet still prevent the contaminating material fromfingering out into the aquifer beyond the edge of the buffer to distant,otherwise uncontaminated, fresh water pumping wells.

SUMMARY OF THE INVENTION Applicant has discovered a method of limitingcontamination in waste disposal wells by injecting a mobility bufferslug consisting of an oil-external or water-external micellar dispersionbefore the contaminating materials. The size of the buffer depends on anestimate of the total waste to be injected over the life of the well.Generally from about 0.1 to about 25 percent formation pore volume(based on the anticipated pore volume necessary to receive the total,anticipated, waste material) and preferably 1-10 percent is useful. Themobility ratio should be favorable, i.e., the mobility of the micellardispersion should be sufficiently low to protect against fingering. Themobility buffer can have mobilities graded from a low at the front to ahigh at the rear, preferably the mobility at the rear is about equal tothe mobility of the waste materials being pumped in the aquifer. Also,the mobilities of the buffer can be graded in a logarithmic fashion astaught in U. S. Pat. No. 3,467,187 to Gogarty et al.

After the mobility buffer is injected into the well, the waste materialis injected. If desired, pumping wells can be drilled ahead of theadvancing buffer front to withdraw the original uncontaminated aquiferfluid.

PREFERRED EMBODIMENTS OF THE INVENTION The mobility buffer is anoil-external or water-external micellar dispersion. The term micellardispersion is meant to include microemulsion, *transparent" emulsion,and micellar solution. The micellar dispersion is composed ofhydrocarbon, aqueous medium, surfactant, and optionally, cosurfactantand/or electrolyte. Other components, e.g., bactericides, corrosioninhibitors, etc. can be added if desired. Examples of volume amountsinclude from 2 percent to about percent hydrocarbon, about 1 percent toabout percent aqueous medium, at least about 4 percent surfactant, about0.01 to about 20 percent or more of cosurfactant (also identified assemi-polar organic compound and cosolubilizer) and about 0.001 to about5 percent or more (based on the aqueous medium) of electrolyte. Thehydrocarbon can be crude oil, a partially refined fraction of crude oil,and refined fractions of crude oil and synthetic hydrocarbons. Thesurfactant can be cationic, anionic or nonionic. The aqueous medium canbe soft water or it can contain salts and can be a relatively brinywater. The cosurfactant can be a monohydric or polyhydric alcohol,ketone, amine, ester, aldehyde, or like compound containing 120.or morecarbon atoms. The electrolyte is preferably inorganic base, inorganicacid or inorganic salt, but any water-soluble electrolyte is useful withthe invention. Examples of specific micellar dispersions useful withthis invention and particular components to make up the micellardispersion can be found in U. S. Pat. No. 3,254,714 to Gogarty et al.;U.S. Pat. No. 3,266,570 to Gogarty; U.S. Pat. No. 3,275,075 to Gogartyet al.; U.S. Pat. No. 3,297,084 to Gogarty et al.; U.S. Pat. No.3,307,628 to Sena; U.S. Pat. No. 3,330,343 to Tosch et al.; U.S. Pat.No. 3,356,138 to Davis et al.; U.S. Pat. No. 3,412,791 to Gogarty; U.S.Pat. No. 3,467,187 to Gogarty et al.; U.S. Pat. No. 3,476,184 to Davis;U.S. Pat. No. 3,497,006 to Jones et al.; U.S. Pat. No. 3,506,070 andU.S. Pat. No. 3,506,071 to Jones; U.S. Pat. No. 3,330,344 and U.S. Pat.No. 3,348,611 to Reisberg; U.S. Pat. No. 3,512,586 to Holm; U.S. Pat.No. 3,373,809 to Cook, Jr. et al., etc. The mobility of the micellardispersion can be adjusted, as taught in the above patents, byregulating the electrolyte content, the cosurfactant, etc. In addition,mobility reducing agents can be incorporated into either the internalphase or the external phase or both phases of the micellar dispersion.For example, oil soluble high molecular weight polymers can beincorporated into the hydrocarbon phase to decrease the mobility, i.e.,increase the viscosity, of the micellar dispersion whereas water-solublemobility agents or viscosity increasing agents can be incorporated intothe water phase of the micellar dispersion to accomplish the sameobjective. Examples of water-soluble agents include polysaccharides,partially hydrolyzed, high molecular weight polyacrylamides such as thePusher polymers marketed by Dow Chemical Company, Midland, Mich., highmolecular weight polymers (especially anionic) which exhibit viscosityincreasing properties or mobility reducing properties, and agents suchas sugars, dextrans, carboxymethylcellulose, I amines, glycerine,alcohols, etc. and mixtures of the above which have sufficient molecularweight character to impart viscosity increasing characteristics to thewater. If it is desirable to inject relatively high viscositydispersions, examples of such micellar dispersions can be found incopending patent application identified as U. S. Ser. No. 20,101 filedMar. 16, 1970 by Marion 0. Son, Jr.

Waste disposal fluids containing strong acids and bases, etc. and evendivalent cations such as calcium and barium in large concentrations mayadversely affect the viscosity characteristics of the micellardispersionj e.g., they may tend to lower its viscosity. Such Idegradation can be inhibited by insulating the micellar dispersion slugfrom the waste materials. Water can be used as the insulating materialor spacer slug. Volume amounts of the spacer slug can be about equal tothe volume of mobility buffer injected. Preferably, the'insulating orspacer fluid injected after the micellar dispersion slug will have amobility about equal to the mobility of the contaminating fluid injectedinto the aquifer, i.e., very small amounts of mobility reducing agentcan be added to the spacer slug.

Preferably, the mobility buffer is injected before the waste material isinjected into the well, however, it is recognized that special mobilitybuffer injection wells can be employed at distant points in the aquiferbetween the central waste disposal well and a distant fresh waterpumping well. This technique conserves the portion of the aquifer stilluncontaminated by the advance of waste disposal fluid. It is alsorecognized that the mobility buffer can be positioned in the aquifer byvarious techniques known to the art such as removing fluids from atleast one other well in fluid communication with the aquifer so as toinduce said mobility buffer to flow into desired positions.

An additional advantage of the micellar dispersion is that it can bedesigned to solubilize hydrocarbon, etc. off of the reservoir rock andthus clean" the reservoir before the contaminating fluid is injected.This may be desired to obtain increased relative permeabilities to theflow of the material within the reservoir, to prevent or inhibitundesired reactions of the contaminating materials with certainmaterials within the reservoir, etc.

It is not intended that this invention be limited by the specificstaught above. Rather, all equivalents obvious to those skilled in theart are intended to be incorporated within the scope of the invention asdefined within the specification and appended claims.

What is claimed is:

l. A process of inhibiting fingering of contaminating fluids in anunderground reservoir wherein the contaminating fluids are injected intothe reservoir through an injection means, the method comprisin injectingmto he reservoir in advance of the con aminating fluids, a micellardispersion having sufficiently low mobility to reduce the fingeringtendency of the contaminating fluids into portions of the reservoir.

2. The process of claim 1 wherein the micellar dispersion is comprisedof hydrocarbon, aqueous medium, and surfactant.

3. The process of claim 2 wherein the micellar dispersion containscosurfactant and/or electrolyte.

4. The process of claim 2 wherein the micellar dispersion is comprisedof about 2 to about percent hydrocarbon, about 1 to about percent waterand at least about 4 percent surfactant, the percents based on volume.

5. The process of claim 1 wherein at least the front portion of themicellar dispersion has a mobility about equal to or less than about themobility of formation fluids in front of the micellar dispersion.

6. The process of claim 1 wherein at least the back portionof themicellar dispersion hasa mobility about equal to or greater than aboutthe mobility of the front portion of the contaminating fluids flowing inthe formation.

7. The process of claim I wherein an aqueous insulating slug is injectedbetween the micellar dispersion and the contaminating fluids to inhibitdegradation of the micellar dispersion by the contaminating fluids.

8. The process of claim 1 wherein the micellar dispersion contains amobility reducing agent in either the hydrocarbon phase or the waterphase, or optionally, both phases.

9. A process of limiting aquifer contamination of waste materials beinginjected into an aquifer through an injection means in fluidcommunication with the aquifer, the method comprising injecting into theaquifer in advance of the waste materials about 0.1 to about 25 percentformation pore volume, based on the anticipated pore volume to beoccupied by the total amount of waste materials to be injected, of amicellar dispersion having a sufficiently low mobility to inhibit thetendency of the waste materials to finger into at least portions of theaquifer.

10. The process of claim 9 wherein the micellar dispersion is comprisedof hydrocarbon, aqueous medium, surfactant, and optionally cosurfactantand/or electrolyte.

11. The process of claim 9 wherein at least the front portion of themicellar dispersion has a mobility about equal to or less than about themobility of the formation fluids flowing ahead of the micellardispersion.

12. The process of claim 9 wherein at least the back portion of themicellar dispersion has a mobility about equal to or greater than aboutthe mobility of the front portion of the waste materials flowing in theformation.

13. The process of claim 9 wherein an aqueous insulating slug isinjected after the micellar dispersion and before the waste materials toprevent at least immediate degradation of the mobility of the micellardispersion. v

2. The process of claim 1 wherein the micellar dispersion is comprisedof hydrocarbon, aqueous medium, and surfactant.
 3. The process of claim2 wherein the micellar dispersion contains cosurfactant and/orelectrolyte.
 4. The process of claim 2 wherein the micellar dispersionis comprised of about 2 to about 90 percent hydrocarbon, about 1 toabout 95 percent water and at least about 4 percent surfactant, thepercents based on volume.
 5. The process of claim 1 wherein at least thefront portion of the micellar dispersion has a mobility about equal toor less than about the mobility of formAtion fluids in front of themicellar dispersion.
 6. The process of claim 1 wherein at least the backportion of the micellar dispersion has a mobility about equal to orgreater than about the mobility of the front portion of thecontaminating fluids flowing in the formation.
 7. The process of claim 1wherein an aqueous insulating slug is injected between the micellardispersion and the contaminating fluids to inhibit degradation of themicellar dispersion by the contaminating fluids.
 8. The process of claim1 wherein the micellar dispersion contains a mobility reducing agent ineither the hydrocarbon phase or the water phase, or optionally, bothphases.
 9. A process of limiting aquifer contamination of wastematerials being injected into an aquifer through an injection means influid communication with the aquifer, the method comprising injectinginto the aquifer in advance of the waste materials about 0.1 to about 25percent formation pore volume, based on the anticipated pore volume tobe occupied by the total amount of waste materials to be injected, of amicellar dispersion having a sufficiently low mobility to inhibit thetendency of the waste materials to finger into at least portions of theaquifer.
 10. The process of claim 9 wherein the micellar dispersion iscomprised of hydrocarbon, aqueous medium, surfactant, and optionallycosurfactant and/or electrolyte.
 11. The process of claim 9 wherein atleast the front portion of the micellar dispersion has a mobility aboutequal to or less than about the mobility of the formation fluids flowingahead of the micellar dispersion.
 12. The process of claim 9 wherein atleast the back portion of the micellar dispersion has a mobility aboutequal to or greater than about the mobility of the front portion of thewaste materials flowing in the formation.
 13. The process of claim 9wherein an aqueous insulating slug is injected after the micellardispersion and before the waste materials to prevent at least immediatedegradation of the mobility of the micellar dispersion.